<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    <title>Title</title>
    <!--<link href="http://libs.baidu.com/bootstrap/3.0.3/css/bootstrap.min.css" rel="stylesheet">
    <script src="http://libs.baidu.com/jquery/2.0.0/jquery.min.js"></script>
    <script src="http://libs.baidu.com/bootstrap/3.0.3/js/bootstrap.min.js"></script>-->
    <style>
        body {
            background-color:lightgreen;
        }

        @media only screen and (max-width: 500px) {
            body {
                background-color:lightblue;
            }
        }
    </style>
</head>
<body>
<p>重置浏览器大小，当文档的宽度小于 500 像素，背景会变为浅蓝色，否则为浅绿色。</p>
</body>
</html>
